In recent years, surgical operations have been widely practiced in the form of endoscopic surgery to improve QOL (Quality of Life), such as reduction in patient's pain, hospitalization period, and size of the scar associated with the surgery. Endoscopic surgery is performed in such a way that an operator inserts forceps or other related tools through a thin tube (trocar) and performs the surgery while observing images from a laparoscope. Since the scar is smaller than that in open surgery, the burden on the patient is smaller. However, since the operator moves the forceps or other related tools using the abdominal wall as a pivotal point, sufficient degrees of freedom are not provided at the tip of the forceps and hence it is not easy to freely approach the site to be treated. Such a situation requires a highly skilled operator. To reduce the burden on the operator, studies on multi-DOF forceps system have been actively underway, in which robotics technology is used to impart multiple degrees of freedom to the tip of forceps.
The master-slave concept used in commercially available multi-DOF forceps systems has advantages of, for example, capability of remotely and intuitively operating the forceps. To provide more accurate, safer workability, it is desirable to provide force feedback to the operator. To this end, studies on forceps with a force sensor provided in the vicinity of the tip of the forceps are underway. However, such a multi-DOF forceps system using electric actuators to drive the master and slave portions not only cannot feed a minute force back to the operator because of a high reduction ratio, but also has an insufficient movable range and results in a bulky apparatus. Further, attaching a force sensor to the forceps is not an easy task in consideration of practical factors, such as reduction in size, sterilization, and calibration.
To address the above problems, studies on a multi-DOF forceps system are underway, in which pneumatic actuators are used to drive the master and slave portions. A pneumatic actuator, which has nonlinear characteristics, is inferior to an electric actuator in terms of controllability, but has advantages of, for example, presenting passive softness, having a high mass-to-output ratio, and producing a large force without a reduction gear train. For example, a multi-DOF forceps system has been proposed (see the non-patent document 1), in which the slave portion includes a 3-DOF forceps manipulator using pneumatic cylinders and the pressure in each of the pneumatic cylinders is used to estimate the external force acting on the tip of the forceps instead of using a force sensor. Further, a multi-DOF forceps system has been proposed (see the non-patent document 2), which includes a 3-DOF pneumatic manipulator that holds and drives the 3-DOF forceps manipulator described in the non-patent document 1 in a region outside the abdomen.
Non-patent document 1: Bilateral control of multi-DOF forceps system having force sensing capability using pneumatic servo technology, Japan Society of Computer Aided Surgery, pp. 25-31, (2005), Kotaro Tadano, Kenji Kawashima Non-patent document 2: Development of master-slave system having force feedback capability using pneumatically-driven multi-DOF forceps: Development of manipulator for holding forceps, Conference on Robotics and Mechatronics, 1A1-A03, (2006), Kotaro Tadano, Kenji Kawashima